$24 FLYING FOXES
of the vertebrae tend to become ankylosed in old individuals ;
the caudals have no processes, but are like those quite at the end
of the series in long-tailed animals. The sternum is keeled for
the better attachment of the pectoral muscles, the chief muscles
of flight. The ribs, which are much flattened, are occasionally
ankylosed together by their margins. There i& a well-developed
clavicle. In the carpus the scaphoid, lunar, and cuneiform are
all fused together. In the hind-limb the fibula is rarely fully
The Bats are divisible into two primary groups, which are
those of the Megachiroptera and the Microchiroptera.
SUB-ORDER 1. MEGACHIROPTERA.
The Pteropodidae are frugivorous Bats, usually of large size.
The chief distinguishing feature is the fact that the molars
are not tubercular, but marked . with a longitudinal furrow,
which is, however, concealed in the genus Pteralopex by cusps.
The palate is continued back behind the molars. The index
finger has three phalanges, and is usually clawed. The ears
Fro. 256.—Sktill of Pteropus fuscus. x f. (After de Blainville.)
are oval, and the two edges are in contact at the base of the
ear. The tail, if present, has nothing to do with the inter-
fetnoral membrane. This group is entirely Old "World in range.
The genus Pt&ropus embraces the creatures known as Flying Poxes.
They are the largest forms in the sub-order, sometimes having
an expanse of wing of 5 feet (this is the case with P. edidis).
The muzzle is long, and the face therefore ff foxy " in appearance.